This invention relates to a circuit for signal transfer between electric circuits formed on respective layers of a laminated multilayer electric circuit in which the electric circuits are packaged at high density and, more particularly, to a signal transfer circuit suitable for signal transfer between adjacent ones of a great number of wafers which are laminated for packaging.
A technique for high-density packaging of electric circuits has hitherto been known wherein a great number of wafers are laminated and a great number of electrodes are provided an on opposing surfaces of laminated wafers so as to be mutually contacted for signal transfer between wafers. This technique of signal transfer based on contacting of the electrodes faces results a problem that the more the number of electrodes increases, the larger than the part of the electrodes which is likely to end in a failure of contact, and is therefore unpractical. As an approach to this problem, a laminated multilayer electric circuit wherein electrodes between adjacent wafers are coupled for signal transfer through capacitance coupling has already been proposed in Japanese patent application Laid-Open No. 2662/81 Laid-Open on Jan. 12, 1981. In this circuit based on capacitance coupling, a change of a signal to be transferred through the capacitance coupling, that is, a signal having a waveform obtained by differentiating the signal is passed through the capacitor. Accordingly, by utilizing the resultant signal, a flip-flop is driven so that the signal to be transferred is reproduced and held in this flip-flop. Considering then the fact that the flip-flop is sensitive to noises, a pair of differential output signals are derived from a signal input signal and used to differentially drive one electrode of either of two pairs of capacitance electrodes, so that charge/discharge currents of the coupling capacitors can be passed without being circulated through power supply wirings between individual wafers, thereby preventing the flip-flop from operating erroneously owing to noises induced in the power supply wirings.
This laminated multilayer electric circuit using a flip-flop as described above suffers however from a delay in signal transfer at the flip-flop and is therefore unsatisfactory from the standpoint of operation speed. In addition, for prevention of erroneous operation of the flip-flop due to noises, the two pairs of capacitance electrodes are employed and driven differentially. Accordingly, this circuit arrangement requires the two pairs of capacitance electrodes in order to transfer a single signal and so it is unsuited for transferring of a large number of signals.